1. Field of Invention
The present invention relates to a reference light generator that is used primarily to determine the degree of horizontality and the degree of verticality at a construction site and the like.
2. Description of Related Art
Japanese Patent Application Laid-Open No. 63-222214 discloses a conventional reference light generator. It will be explained with reference to FIGS. 15 (Prior Art) and 16 (Prior Art), the reference light generator according to the conventional art will be explained. FIG. 15 (Prior Art) is a cross-sectional view of the reference light generator. FIG. 16 (Prior Art) is similarly a cross-sectional view of the reference light generator, but in a state in which it is inclined at an angle .theta.1. The reference light generator is built in a main body 61. It includes a laser diode 1 serving as a light source, emits a visible light laser beam, a collimator lens 2, a sealed transparent container 63 in which silicon oils 71 and 72, or other suitable liquid are sealed. Silicon oils 71 and 72 having free liquid surfaces 71A and 72A, respectively, are sealed in the container 63, which is divided into two compartments. Light transmission parts 63A, 63B, and 63C of the container 63 are all parallel planes, and are installed so as to orthogonally intersect the optical axis of the laser beam. Light emitted from the laser diode 1 is transformed into a parallel light beam by the collimator lens 2, passes through the silicon oils 71 and 72 inside the sealed transparent container 63, and is guided downward through an aperture 61A at the bottom of the main body 61.
When the optical axis of the laser beam coincides with the direction of gravity, the free surfaces of the silicon oils 71 and 72 become parallel with respect to the light transmission parts 63A through 63C of the transparent container 63. In this case, the laser beam that is emitted from the laser diode 1 passes through the light transmission parts 63A through 63C of the transparent container 63. Then, the laser beam passes through parallel planes that are formed by the silicon oils 71 and 72, and finally is guided vertically downward along an optical path 1A without having its optical path bent.
A leveling device 62 is installed at the base of the reference light generator shown in FIG. 15 (Prior Art). Then, based on bubble pipe displays of leveling device 62, not shown in the drawing, the degree of horizontality is determined crudely so that the inclination of the reference light generator stays within a correctable angular range.
With reference to FIG. 16 (Prior Art), the operation of the reference light generator shown in FIG. 15 (Prior Art) when it is inclined by the angle .theta.1 will be explained. The free surfaces 71A and 72A of the silicon oils 71 and 72 maintain their level surfaces by the action of the gravitational force. Thus, as shown in FIG. 16 (Prior Art), the silicon oils 71 and 72 exhibit the shape of a wedge having an inclination angle .theta.1.
Then, the laser beam is bent by a deflection angle .theta.2 with respect to the optical path 1A along which the laser beam travels before passing through the transparent container 63. The prism effect of the wedge-shaped silicon oils 71 and 72 refracts the laser beam when it passes through the silicon oils 71 and 72. Then, the laser beam is bent by a deflection angle .theta.2 with respect to the optical path 1A along which the laser beam travels before passing through the transparent container 63. Finally, the laser beam is emitted along an optical path 1B out of the main body 61.
The refractive indices of the silicon oils 71 and 72 are denoted by n1 and n2. The relation between the inclination angle .theta.1 of the reference light generator and the deflection angle .theta.2 of the laser beam is expressed by EQU .theta.2=(n1+n2-2)..theta.1.
This equation yields the identity
.theta.2=.theta.1, when n1=n2=1.500.
In this way, the inclination of the reference light generator can be corrected, and the laser beam can always be emitted vertically downward.
The laser beam that has been guided vertically downward is reflected in an orthogonal direction by a pentagonal prism not shown in the drawing, and is transmitted in a horizontal direction. In addition, this pentagonal prism is rotated at a prescribed rotational speed so as to have the optical path 1A coincide with the rotation axis of the pentagonal prism. In this way, a laser beam that scans along a horizontal plane can be obtained. Then, the degree of horizontality at a construction site can be easily determined by illuminating a wall surface and the like with this laser beam and by marking the laser beam.
Although not shown in the drawing, a mechanical-type reference light generator is also known. The mechanical-type reference light generator mechanically corrects the emission direction of the light source based on the inclination angle information of the reference light generator to be obtained from an inclination angle sensor, instead of correcting the inclination of the reference light generator using liquids as discussed in the above.
However, the only laser beam scan plane obtainable with the reference light generator shown in FIGS. 15 (Prior Art) and 16 (Prior Art), or the mechanical-type reference light generator is a horizontal plane. Hence, when determining the degree of horizontality and the degree of verticality, two apparatuses must be prepared, namely, one for determining the degree of horizontality and another for determining the degree of verticality. Moreover, in the manufacturing process of a mechanical-type reference light generator, the emission position of the reference light generator requires precise adjustment. This requirement sometimes becomes a factor that increases the manufacturing cost. Moreover, when an intense shock is applied to the mechanical-type reference light generator, the accuracy of the reference light generator is lost, and the emission position of the reference light generator has to be re-adjusted.